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There are all kinds of locks and alarms that you can make. You can make alarms that are controlled with keys, keypads, remote controls, scanners, or anything else that you can think of. Just for fun, I designed an alarm that is controlled by resistors.

This is a basic motion sensing alarm that detects when someone enters the area. When an intruder is detected, it activates a siren. But what makes this system unique is that it is activated and deactivated by touching a resistor to a pair of metal contacts on the housing. This makes for an interesting kind of security system.

Step 1: Watch the Video

Here is a video walkthrough of the project.

<p>Hi,</p><p>I am making this as a school project. I did the prototyping on the breadboard but the alarm just doesn't work. It goes off randomly or doesn't go off at all. I checked my PIR motion sensor and it is working properly. The code I'm using to program my arduino is the same posted on this instructable.</p><p>Any help or suggestions are welcome. The due date is approaching! :)</p>
<p>hello, i have a question regarding the sensor. can i use accelerometer instead of the pir sensor ?</p>
<p>Very Cool... Got my votes!...</p>
What would be interesting to see is a system with different resistor values for different users, so it could identify the login. A physical username, in a way. Very cool.
Good idea. All it would take is adding a few lines of code.
<p>Really cool idea. Will be trying this. Thanks!!!</p>
<p>This is great! Physical encryption is so interesting.</p>

About This Instructable

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Bio: My name is Jason Poel Smith I am a Community Manager here at Instructables. In my free time, I am an Inventor, Maker, Hacker, Tinker ... More »
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